1. Field of the Invention
This invention relates to circuit breakers in general, and in particular, to circuit breakers with an indicator signaling that the circuit breaker has opened due to an abnormal condition in the protected circuit.
2. Background Information
A type of small circuit breaker, often referred to as a miniature circuit breaker, widely used in residential, light commercial and other applications, has a thermal/magnetic trip device that opens the circuit breaker contacts in response to persistent overload conditions and to short circuits. Many such miniature circuit breakers have a handle that is manually used to turn the circuit breaker off and on and that assumes a position intermediate the off and on positions to signal that the circuit breaker has tripped open. In other such miniature circuit breakers, the handle only has two positions, on and off, the latter of which is assumed when the breaker is manually turned off or when a trip occurs. Thus, in these breakers, the position of the handle does not provide a visual indication of a trip. This can make it difficult to identify a circuit breaker that has tripped among the many circuit breakers in a load center where one or more could have been manually turned off.
It is known to provide a trip flag in a miniature circuit breaker to indicate the tripped condition. Typically, the trip flag is actuated to the tripped condition by a cradle that couples the trip mechanism to the contact assembly to open the circuit breaker. Typically also, the flag is reset following a trip by relatch of the cradle through movement of the handle.
Some miniature circuit breakers automatically reset following a trip. That is, a reset spring relatches the cradle, although the contacts remain open and must be manually reset. As the relatching occurs immediately after the trip, a trip flag that is reset by the cradle would not provide any meaningful trip indication.
There is a need, therefore for an improved arrangement for displaying the trip status of a circuit breaker, and particularly of a circuit breaker that automatically relatches the cradle following a trip.
This need, and others, are satisfied by the invention which is directed to a circuit breaker that includes a trip indicator comprising a trip indicating member carrying trip indicia, such as a flag, which is moved to a tripped position where it is visible through a window in the housing of the circuit breaker by movement of the cradle to the unlatched position in response to actuation of the trip mechanism. The trip indicating member is moved back to the untripped position by movement of the circuit breaker operating member that incorporates the handle to the closed position. Thus, the trip indicator is set to the tripped position by the unlatching of the cradle, however, it is reset not by the relatching of the cradle but instead by the operating member through movement of the handle to the closed position. Although not so limited, it makes the invention useful in connection with circuit breakers in which the cradle is automatically reset following a trip. The trip indicator remains in the tripped position, even though the cradle is relatched, until the operating member is manually moved to the closed position.
The invention accommodates the blow open feature often provided on circuit breakers. The strong magnetic fields created by a short circuit cause the contact arm carrying a movable contact to swing open before the trip mechanism has time to respond. As the cradle has not yet unlatched, the trip indicator remains in the untripped position. However, the handle, being connected to the contact arm moves toward the off position. This movement of the handle toward the off position with the trip indicator in the untripped condition produces interference between the operating member and the trip indicator. In accordance with the invention, the trip indicating member is compliantly displaceable to allow the handle to be moved to the off position following a blow open. When the trip mechanism finally actuates, the cradle is unlatched and spring driven to the tripped position thereby setting the trip indicator to the tripped condition. The handle may then be repositioned to the on position to reclose the circuit breaker and at the same time reset the trip indicating member to the untripped position.
More particularly, the invention is directed to a circuit breaker comprising: a housing; a pair of contacts comprising a fixed contact and a movable contact; an operating member pivotally mounted for movement between a closed position and an open position and having a handle extending outside the housing, and a contact arm carrying the movable contact at a first end and coupled to the operating member at a second end. The circuit breaker further comprises a trip mechanism comprising a thermal/magnetic trip device having a tripped state and an untripped state, a cradle pivotally mounted for movement between a latched position in which the cradle is retained by the trip mechanism in the untripped state and an unlatched position to which the cradle moves when the trip mechanism goes to the tripped state, and an operating spring between the cradle and the contact arm biasing the contact arm to a closed state in which the movable contact engages the fixed contact when the operating member is in the closed state and the cradle is latched and otherwise biasing the contact arm to an open state in which the pair of contacts are separated. A trip indicator for the circuit breaker comprises an indicator window in the housing, a trip indicating member carrying a trip indicia, and an indicator mount mounting the trip indicating member for movement between a tripped position in which the trip indicia is visible through the indicator window and an untripped position in which the trip indicia is not visible through the indicator window. The cradle has an engagement member engaging the trip indicating member and moving the trip indicating member to the tripped position as the cradle moves to the unlatched position. The operating member has a reset member engaging and moving the trip indicating member to the untripped position as the operator is moved to the closed or on position.